Abstract: There is provided a drive for an orbital nozzle comprising a housing having a fluid inlet and containing a fluid driveable impeller from which the fluid, in use of the drive, flows through a passage within the housing, an epicyclic rotary speed reducing mechanism in the housing, an output shaft driven by the epicyclic at speed reduced below the impeller speed, an element driveable by the output shaft mounting the nozzle for rotation, including an element for delivering fluid from the passage to the nozzle, as well as an orbital nozzle unit which incorporates such a drive and a hydraulic cleaning head which incorporates such a drive or orbital nozzle unit.